The present invention generally relates to variable transmission windows. More specifically, the present invention relates to systems and methods for switching the operation of such windows.
Variable transmittance electro-optic (EO) systems, such as electrochromic (EC) cell-based optical filters, have been proposed for use in architectural windows, skylights, and in windows, sunroofs, and rearview mirrors for automobiles. Such EC systems reduce the transmittance of direct or reflected sunlight during daytime through the EC cell in response to the amount of light incident upon the EC cell. Not only do such light filters reduce bothersome glare and ambient brightness, they also reduce fading and heat caused by transmission of sunlight through the window.
A particular incarnation of the EC cell-based optical filters—a variable transmission window—has not been widely accepted commercially for several reasons. First, such a window tends to be rather expensive due to the cost of materials required for its construction and manufacture, and the complexity of construction makes mass-production somewhat complicated. Additionally, EC windows tend to have lower life expectancy than conventional windows due to degradation of the EC materials used in the EC cells. The combination of added cost and lower life expectancy has deterred many architects, designers, and builders from using electrochromic windows.
The commercial use of variable transmission windows in vehicles designed for the transportation of passengers, such as, for example, busses, airplanes, trains, ships, and automobiles, is not common yet either.